1. Field of the Invention
The present invention relates generally to a dual-mode mobile terminal and a method for handover between communication networks using different mobile communication technologies to provide communication services.
2. Description of the Related Art
Currently, Code Division Multiple Access (CDMA) systems are distributed in a wide variety of service areas and equipped with complete infrastructures. However, a third generation communication network, such as a Wideband Code Division Multiple Access (WCDMA) system, has been gradually introduced in order to provide communication services that a second generation communication network, such as CDMA system, cannot provide. Meanwhile, dual-mode mobile terminals have been developed that are capable of providing specific services in a third generation network area while using infrastructure of the second generation network.
Recently, a requirement for mobile terminals capable of operating in all the WCDMA and CDMA systems has driven the development of a dual-mode mobile terminal supporting both of the WCDMA and CDMA systems. The dual-mode mobile terminal requires various technologies optimally compatible with the two modes. Among those technologies, there is roaming for a handover between the WCDMA and CDMA modes in the mobile terminal.
The handover function of the dual-mode mobile terminal enables the mobile terminal to convert the two modes of WCDMA and CDMA into each other. That is, while operating in the WCDMA mode in an area in which the WCDMA service is available, the mobile terminal converts the WCDMA mode into the CDMA mode when a user gets out of the WCDMA service area.
FIG. 1 is a schematic view illustrating an area in which conventional CDMA and WCDMA communication networks are set. Referring to FIG. 1, the area having the CDMA and WCDMA communication networks is divided into a dedicated CDMA service area and an overlapping service area in which all CDMA and WCDMA services are supportable.
When a user enters the CDMA service area 150 during an operation of the dual-mode mobile terminal 100 in the WCDMA mode in the overlapping service area 160, the mobile terminal fails to find a WCDMA base station and scans for a CDMA base station. When the mobile terminal finds the CDMA base station, the mobile terminal converts the WCDMA mode into the CDMA mode and completes a handover. However, when the user moves from the CDMA service area to the overlapping service area 160, the mobile terminal 100 performs the handover in order to convert the CDMA mode into the WCDMA mode according to certain conditions.
Nevertheless, when the user moves from one communication network to another while the dual-mode mobile terminal 100 communicates with the one communication network for a packet service, the mobile terminal does not perform a handover of a Packet Service call (PS call). That is, when the user moves from one communication network to another while communicating with one of the communication networks to obtain packet service, the dual-mode mobile terminal 100 interrupts the communication with the previous communication network to obtain the packet service and performs an initialization for a PS call in order to communicate with another communication network for a packet service.
As described above, in order to perform the handover from one communication network to another during the packet service communication of the mobile terminal, the mobile terminal interrupts its_connection to the previous communication network and communicates with a new communication network for the packet service communication. Consequently, there is a problem in that when a user moves in different communication networks during the operation of the mobile terminal for the packet service communication, the mobile terminal cannot continuously receive packet service data.